I remember interviews with Panasonic engineers saying that they would not be using on sensor PDAF. But the EM-1 does. So this appears to not add up well.

the same sensor can be supplied with different CFAs on top of it to accomplish the PDAF... so you are talking about camera engineers, not sensor engineers... Olympus paid for a different CFA (with some locations dedicated to PDAF use) on top of sensors for E-M1 and got what they paid for...

What is the source of this info? PDAF sensors have to be electrically connected to something.